This proposal is for a controlled intervention trial to reduce substance use and risky sexual behavior among White and African-American homosexually-active men. Patterns of sexual behaviors that confer risk for contracting or transmitting HIV infection are influenced by a variety of sociocultural and situational factors, including recreational non-injection substance use. Many studies have identified general patterns of association between substance use and continued high-risk sexual behaviors. However, we are still learning about the specific casual mechanisms responsible for these associations. As a result, the efficacy of behavioral interventions targeted at preventing risky sex in the context of substance use has not been rigorously tested. The proposed study has two specific aims; 1) explore the mechanisms which link substance use to risky sex among White, African-American, and latino gay men; and 2) develop and test intervention strategies specifically designed to prevent lapses to risky sex in the context of substance use among White and African-American gay men. Successful completion of this study and dissemination of its findings have the potential for the prevention of future waves of AIDS among at-risk homosexually-active populations. The proposed four-year study is divided into three phases: 1) a none-year formative research phase during which qualitative and quantitative methods will be used to identify specific relationships between substance use and risky sex and the sociocultural contexts in which those associations take place among 50 White, 50 African-American, and 50 Latino gay men; 2) a two- year phase for a controlled intervention trial that compares a state-of-the art cognitive-behavioral/skills development sexual behavior change intervention with an experimental intervention specifically aimed at altering substance use and risky sex among 250 White and 250 African- American gay men; and 3) a one year analytical phase to refine the experimental intervention and use statistical, mathematical, and economic modeling to identify cost-effective strategies for targeted field replication and dissemination activities.